1. Field of the Invention
The present invention relates to a biological information detection apparatus which detects biological information of a human being or an animal.
2. Related Art
At the present time, there has been proposed a sleepiness alarm system which judges the sleepiness state of a driver who is driving a vehicle by measuring a biological information such as heart rate, pulsebeat, respiration, temperature, skin resistance and blood pressure of the driver and notifies the driver of the sleepiness state. Electrodes which detect biological information from hands of the driver are attached to a steering wheel of a vehicle having such a sleepiness alarm system mounted thereon. Therefore, the driver must always touch the electrodes and consequently the driver is forced to undergo an excessive burden. Therefore, even if the driver temporarily releases one hand or both hands from the electrodes, a heart rate detection apparatus capable of correctly detecting the heart rate serving as biological information of the driver has been proposed. See, for example, Japanese Patent Application Laid-Open Publication No. Hei-06-255518. If the driver temporarily releases one hand or both hands from the electrodes attached to the steering wheel and consequently the heart rate signal from the electrodes is missing in such a heart rate detection apparatus, the missing section of the heart rate signal is compensated for by using a heart rate signal obtained after recovery.
If the time over which the driver releases one hand or both hands from the electrodes becomes long in such a heart rate detection apparatus, however, the time when processing is conducted to compensate for the missing section of the heart rate signal is delayed. This results in a problem that the measurement of the heart rate is stopped over this time period.